1. Field of the Invention
The present invention relates to the process of the recovery of underground natural gas and oil by hydraulic fracturing and more particularly to a method for removing contaminants from the wastewater produced by the hydraulic fracturing process.
2. Description of Prior Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
High-volume horizontal hydraulic fracturing, also known as “hydrofracking,” is a well-known drilling process for extracting natural gas and oil from underground shale rock deposits. The hydrofracking process includes injecting substantial quantities of a fracturing fluid consisting of water, mixed with sand or other base particles (known as “proppants”) and other chemicals into the shale formations at high pressures to create, expand or extend fissures by breaking up the rock in order to release the gas or oil deposits captured in the shale matrix. The pressure in the rock and pumps cause the fracturing fluid to flow back through the well to the surface where it is collected. Then, the natural gas or oil can flow from the fractured shale deposit back through the pipe and be collected at the surface.
While the hydrofracturing process is very good at releasing natural gas and oil deposits that otherwise would be uneconomical to recover from the shale formulations, the disposal of the wastewater used in the process creates serious environmental issues because it is contaminated with various chemicals, some of which are toxic, as well as radioactive substances including radium and other radionuclides. As a result, the Environmental Protection Agency and other governmental agencies have become involved in monitoring the hydrofracking processes being carried out because the resulting wastewater often ends up in the water supply without appropriate treatment. That is a result of the wastewater either being processed in sewerage processing plants not designed to treat water with those types of contaminants or having no treatment at all. The wastewater may eventually be released into rivers that supply drinking water to the public. It may also end up in aquifers, surface ponds and lakes or be sent to injection wells for disposal.
The present invention relates a simple method of safely and economically removing contaminants from the wastewater resulting from the hydrofracking process. The invention has the advantage of not requiring the disposal of the removed contaminants, which may be toxic, radioactive or both, because the removed contaminants remain underground permanently. The contaminants are either captured in the coating of the proppants which are permanently lodged in the fractured shale deposits or are captured in the coating of the surface of the pipe in the borehole which remains in place in the ground after the gas or oil removal process is completed.
It is therefore a prime object of the present invention to provide a method of recovery of underground natural gas and oil by hydraulic fracturing.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from the wastewater before the wastewater returns to the surface.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a contaminant-capturing substance which is situated and remains below the surface of the ground.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a contaminant-capturing substance which can be deposited in the pipe either before or after the pipe is placed in the ground.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a pipe with one or more sections coated with a contaminant-capturing substance.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a pipe with sections coated with different contaminant-capturing substances.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a pipe with spaced sections coated with the same or different contaminant-capturing substances.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a coated portion of the pipe.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a pipe with a liner containing a contaminant-capturing substance.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a pipe that is coated with multiple layers of a contaminant-capturing substance.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a pipe having a coating of contaminant-capturing substance sprayed on the interior surface of the pipe.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a contaminant-capturing substance coated on the interior surface of the pipe having a layer which increases the surface area of the pipe surface.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a contaminant-capturing substance coated pipe in which turbulence in the wastewater is created.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing a customized mixture of contaminant-capturing substances.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing proppants coated with a contaminant-capturing substance.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing layers of proppants coated with different contaminant-capturing substances.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing layers of proppants, wherein the proppants in at least one of the layers are not coated with a contaminant-capturing substance, and the proppants in another layer are coated with a contaminant-capturing substance.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing proppants and ion exchange resins or other sequestering agents, either intermixed or in layers.
It is another object of the present invention to provide a method of hydraulic fracturing in which contaminants are removed from wastewater utilizing pipes coated with a contaminant-capturing substance wherein compressed air or other gas is used to create bubbles to prevent the build-up of dissolved solids over the coating which reduce the contaminant-capturing ability of the substance.